1. Field of the Invention
In one of its aspects, the present invention relates to a balloon dilation catheter. In another of its aspects, the present invention relates to a catheterization method.
2. Brief Description of the Prior Art
Balloon dilation catheters have been known for many years. Originally, such catheters were used in interventional techniques such as angioplasty.
In recent years, balloon dilation catheters have also been used to facilitate delivery of endovascular prosthesis' such as stents. Stents are generally known. Indeed, the term “stent” has been used interchangeably with terms such as “intraluminal vascular graft” and “expansible prosthesis”. As used throughout this specification, the term “stent” is intended to have a broad meaning and encompasses any expandable prosthetic device for implantation in a body passageway (e.g., a lumen or artery).
In the past dozen years, the use of stents has attracted an increasing amount of attention due to the potential of these devices to be used, in certain cases, as an alternative to surgery. Generally, a stent is used to obtain and maintain the patency of the body passageway while maintaining the integrity of the passageway. As used in this specification, the term “body passageway” is intended to have a broad meaning and encompasses any duct (e.g., natural or iatrogenic) within the human body and can include a member selected from the group comprising: blood vessels, respiratory ducts, gastrointestinal ducts and the like.
Stent development has evolved to the point where the vast majority of currently available stents rely on controlled plastic deformation of the entire structure of the stent at the target body passageway so that only sufficient force to maintain the patency of the body passageway is applied during expansion of the stent.
Generally, in many of these systems, a stent, in association with a balloon, is delivered to the target area of the body passageway by a catheter system. Once the stent has been properly located (for example, for intravascular implantation the target area of the vessel can be filled with a contrast medium to facilitate visualization during fluoroscopy), the balloon is expanded thereby plastically deforming the entire structure of the stent so that the latter is urged in place against the body passageway. As indicated above, the amount of force applied is at least that necessary to expand the stent (i.e., the applied force exceeds the minimum force above which the stent material will undergo plastic deformation) while maintaining the patency of the body passageway. At this point, the balloon is deflated and withdrawn within the catheter, and is subsequently removed. Ideally, the stent will remain in place and maintain the target area of the body passageway substantially free of blockage (or narrowing).
See, for example, any of the following patents:
U.S. Pat. No. 4,323,071 (Simpson et al.),
U.S. Pat. No. 4,411,055 (Simpson et al.),
U.S. Pat. No. 4,616,648 (Simpson),
U.S. Pat. No. 4,661,094 (Simpson),
U.S. Pat. No. 4,733,665 (Palmaz),
U.S. Pat. No. 4,739,762 (Palmaz),
U.S. Pat. No. 4,800,882 (Gianturco),
U.S. Pat. No. 4,907,336 (Gianturco),
U.S. Pat. No. 5,035,706 (Gianturco et al.),
U.S. Pat. No. 5,037,392 (Hillstead),
U.S. Pat. No. 5,041,126 (Gianturco),
U.S. Pat. No. 5,092,873 (Simpson et al.),
U.S. Pat. No. 5,102,417 (Palmaz),
U.S. Pat. No. 5,147,385 (Beck et al.),
U.S. Pat. No. 5,269,793 (Simpson),
U.S. Pat. No. 5,282,824 (Gianturco),
U.S. Pat. No. 5,316,023 (Palmaz et al.),
U.S. Pat. No. 5,415,634 (Glynn et al.),
U.S. Pat. No. 5,462,529 (Simpson et al.),
U.S. Pat. No. 5,755,771 (Penn et al.),
U.S. Pat. No. 5,980,570 (Simpson),
International patent application PCT/CA97/00151 (Penn et al.), and
International patent application PCT/CA97/00152 (Penn et al.),
for a discussion on previous stent designs and deployment systems.
Given the development of stent design, the prior art has also focussed on delivery systems for stent deployment.
One particular delivery system is taught by U.S. Pat. No. 4,748,982 [Horzewski et al. (Horzewski)]. Horzewski teaches a reinforced balloon dilation catheter with a slitted exchange sleeve. Essentially, the catheter comprises a tubular member having a first lumen and a second lumen. A dilation balloon is mounted on the distal end of the tubular member and is in communication with the first lumen. An opening (or notch) is disposed in the tubular member intermediate its proximal and distal ends for receiving a guidewire which travels through the second lumen and emanates out of the distal end of the tubular member. A slit is disposed on the longitudinal portion of the tubular member between the opening and an area 0.5-1 cm proximal the dilation balloon. Thus, as illustrated in FIG. 1 of Horzewski, the guidewire travels partly within a lumen in the catheter (approximately 10-15 cm) and partly along the outside of the catheter (approximately 80-90 cm). This approach is also known as a “monorail” delivery system. The principal advantage of this approach is that it permits so-called “rapid exchange” of the balloon catheter with another balloon catheter. In design, the exchange is facilitated by the provision of the above-mentioned slit so that the actual exchange is done over the balloon portion only (approximately 3 cm). The principal disadvantages of this approach include: less than optimum steerability of the guidewire, difficulties in moving the guidewire with respect to the catheter, less than optimum torque control and inability to exchange the guidewire while leaving the catheter in place. The catheter illustrated by Horzewski has not gained widespread commercial popularity.
Another approach for catheterization is the so-called “over the wire” approach—this approach is discussed in many of the above-mentioned United States patents naming John P. Simpson as an inventor. In this approach, the catheter comprises a tubular member having a first lumen and a second lumen. A dilation balloon is mounted on the distal end of the tubular member and is in communication with the first lumen. The second lumen runs through the length of the tubular member. An opening is disposed in the tubular member at its proximal end for receiving a guidewire which travels through second lumen and emanates out of the distal end of the tubular member. Thus, in the “over the wire” approach, the guidewire is encompassed by the second lumen along the entire length of the tubular member (approximately 90-105 cm). The principal advantages of the this approach include: optimum steerability, smoother movement of the guidewire with respect to the catheter (due to the coaxial relationship thereof), optimum torque control and the ability to exchange the guidewire while leaving the catheter in place. The principal is disadvantage of this approach is that exchange with another balloon catheter is relatively cumbersome (i.e., compared to the “monorail” approach discussed above.
A purported improvement over the “monorail” delivery system is described in U.S. Pat. No. 5,195,978 [Schiffer]. Schiffer teaches a “rapid exchange over-the-wire catheter”. The purported point of novelty in Schiffer is the provision of one or more breakaway elements for progressively exposing the guidewire from the proximal end toward the distal end of the catheter. In the illustrated embodiment the breakaway element is a pull tab or tear strip. The tab strip form from a plurality of longitudinally extending generally parallel grooves form in the tubular shaft of the catheter. The Schiffer catheter is disadvantageous since it requires the physician to execute two distinct and sequential steps to achieve “rapid exchange”. First, the physician must take one hand off the guidewire or the catheter and thereafter grasp and remove the pull tab or tear strip to expose the guidewire. Second, the physician must remove the catheter while the guidewire is held in position. The requirement for these two distinct and sequential steps renders the Schiffer catheter cumbersome, time consuming and impractical to use.
Accordingly, it would be desirable to have a balloon dilation catheter which combined the advantages of the above-mentioned “monorail” approach and “over the wire” approach while obviating or mitigating the disadvantages of these approaches. It would be further advantageous if the balloon dilation catheter were readily adaptable to be used in various interventional techniques such as endovascular prosthesis delivery, angioplasty and the like.